Palladium-free aminocarbonylation of aryl, benzyl, and styryl iodides and bromides by amines using Mo(CO)6 and norbornadiene

Article abstract of DOI:10.1016/j.tet.2012.10.002

A simple and efficient method is described for aminocarbonylation of aryl, benzyl, and styryl iodides and bromides using the in situ generated molybdenum tetracarbonyl norbornadiene [Mo(CO)₄(nbd)] complex as a suitable source of carbon monoxide.

Full text of DOI:10.1016/j.tet.2012.10.002

Tetrahedron 69 (2013) 418e426
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Palladium-free aminocarbonylation of aryl, benzyl, and styryl iodides
and bromides by amines using Mo(CO)6 and norbornadiene
*
*
Nasser Iranpoor , Habib Firouzabadi , Somayeh Motevalli, Mohsen Talebi
Chemistry Department, College of Sciences, Shiraz University, Shiraz 71454, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 March 2012
Received in revised form 2 September 2012
Accepted 2 October 2012
Available online 6 October 2012
A simple and efficient method is described for aminocarbonylation of aryl, benzyl, and styryl iodides and
bromides using the in situ generated molybdenum tetracarbonyl norbornadiene [Mo(CO)4(nbd)] com-
plex as a suitable source of carbon monoxide.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Aminocarbonylation
Molybdenum hexacarbonyl
Aryl halide
Amine
Amide
1. Introduction
dimethylaminocarbonylation of aryl and alkenyl iodides using
DMF under strongly basic conditions,8 or DMF/POCl3 have been
Due to the importance of amides and their great application in
medicinal chemistry,1 several methods have been developed for
their preparation. The classical method of synthesis of these com-
pounds is based on the aminolysis of a reactive carboxy derivative
such as an acid chloride, anhydride or acyl azide.2 Moreover, cata-
lytic systems have been developed without requirement to activate
the carboxylic acids.3 One of these catalytic methods involves the
preparation of amides through aminocarbonylation of organic ha-
lides in the presence of CO and an amine using catalytic amounts of
a transition metal based catalyst. Firstly, palladium-catalyzed car-
bonylation of aryl and alkenyl halides was reported by Heck in 1974
using carbon monoxide and different amines.4 After this report,
much effort was directed to develop the use of gaseous carbon
monoxide for the preparation of amides using various transition
metal catalysts and amines.5 Due to drawbacks of using the toxic
gaseous CO, chemists assay to develop CO-free methods or use
indirect sources of carbon monoxide. After the first report of Tsuji
et al. on the use of formamides as a carbonyl source in carbonyla-
tion,6 Kondo et al. subsequently developed a carbon monoxide-free
carbonylation reaction by using formamides and [PPN]
[Ru3H(CO)11]/PCy3 catalyst system.7 Recently, palladium-catalyzed
reported in the literature.9 After the early report of Corey and
Hegedus on the use of hazardous low boiling point Ni(CO)4 for
aminocarbonylation reaction of vinyl bromides,10 the less harmful
Mo(CO)6, Cr(CO)6 and W(CO)6 were applied to the palladium-
catalyzed carbonylation of organic halides under both thermal
and microwave conditions.11 In 2009, Yamane et al. prepared
benzylamine
molybdenum
pentacarbonyl
complex
[PhCH2NH2Mo(CO)5] in 50% yield from the intermediate
Mo(CO)5ClNEt4 and interestingly applied it in the presence of a base
and catalytic amounts of a palladium(0) complex for benzylami-
nocarbonylation of aryl bromides and iodides to afford their cor-
responding benzylamides.12 Later, the same group found that
amides can be obtained even without palladium catalyst when the
reactions were performed at higher temperature in the presence of
13
Mo(CO)5ClNEt4 and also using the in situ generated Mo(CO)5Cl-
NEt4 using 0.2 equiv of Mo(CO)6.14 In this work we report a simple
and efficient method for the one-pot aminocarbonylation of aryl,
benzyl, and styryl iodides and bromides using the in situ generated
Mo(CO)4(nbd) complex in the absence of a Pd catalyst.
2. Result and discussion
In order to avoid the use of pre-prepared amineeMo(CO)5
complex as an intermediate for the aminocarbonylation re-
action,12,13 we decided to investigate the possibility of using
Mo(CO)6 in conjunction with different complexing agents for
* Corresponding authors. Tel.: þ98 711 2287600; fax: þ98 711 2280926; e-mail
addresses: iranpoor@chem.susc.ac.ir (N. Iranpoor), firouzabadi@chem.susc.ac.ir (H.
Firouzabadi).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.10.002

N. Iranpoor et al. / Tetrahedron 69 (2013) 418e426
419
aminocarbonylation of aryl halides. For this purpose, it seemed
necessary first to find the most suitable reaction conditions for the
reaction with Mo(CO)6. For optimization of the reaction conditions,
we first performed the aminocarbonylation of iodobenzene with
benzylamine in the presence of Mo(CO)6 as the model reaction and
the effects of the different parameters were studied. Several bases
were screened for this reaction. Initially, 1,8-diazabicyclo[5.4.0]
undec-7-ene (DBU) was utilized as a base due to both its strong
basicity and also its efficiency to replace the CO group to form the
DBUemolybdenum carbonyl complex.11b The reaction was carried
out at 140 ꢀC in diglyme as solvent and the desired product was
obtained in moderate yield (Table 1, entry 1). Then DBU was
substituted by bases such as 1,4-diazabicyclo[2.2.2]octane (DABCO)
and n-Pr3N. Although the obtained yields were almost similar, but
the reactions time was dramatically increased up to 10 h when
using n-Pr3N (Table 1, entry 2) and reduced to 1 h in the case of
using DABCO (Table 1, entry 3). When we did the reaction in molten
salts such as tetrabutyl ammonium bromide (TBAB) or n-butyl-
methylimidazolium bromide (BMIMBr) in the presence of n-Pr3N as
the base, some improvement was observed and the reaction time
was decreased from 10 to 3 h in the case of using TBAB (Table 1,
entry 4). Since the presence of TBAB improved the yield of the re-
action, it was decided to investigate its effect on the amino-
carbonylation reaction of iodobenzene with benzylamine and
Mo(CO)6 in the presence of DBU, n-Pr3N, and DABCO in diglyme as
solvent (Table 1, entries 7e9). Among the different bases, which
were studied, an excellent yield of 3aa was obtained in the presence
of DABCO with the shortest reaction time (Table 1, entry 9). De-
creasing the amount of DABCO from three equimolar to two and
one equimolar increases the reaction time from 45 min to 6 and 7 h,
respectively (Table 1, entries 21 and 22). So far, these studies
showed that the mixture of TBAB, DABCO, and Mo(CO)6 is the most
suitable reagent system for aminocarbonylation of benzylamine in
diglyme. Since, in a recent report for this reaction,13 tetraethyl
ammonium chloride has been used, we decided to study its effect
on the progress of the reaction under our optimized conditions.
When TBAB was replaced with tetraethyl ammonium chloride
(TEAC), monitoring of the reaction showed the formation of only
trace amounts of the product, which shows the inefficiency of TEAC
compared to TBAB (Table 1, entry 10). We also studied the use of
excess benzylamine to act both as base and reactant with and
without TBAB in diglyme. However, the reactions were not com-
pleted even after 24 h (Table 1, entries 19 and 20). The effect of
other solvents such as DMF, DMSO, and toluene were also studied,
but none of them were found to be as suitable as diglyme (Table 1,
entries 9, 16e18). From this study the result of entry 9 was found to
be the optimum conditions for this reaction. In order to see the
possibility of using catalytic amounts of Mo(CO)6, a reaction was
performed using 0.2 equiv of Mo(CO)6, however the reaction was
not completed and majority of the starting material was recovered
unchanged (Table 1, entry 11). Since there is a very recent report for
the aminocarbonylation using about 0.2 equiv of Mo(CO)6 and
tetraethyl ammonium chloride,14 we also repeated this reaction for
iodobenzene and benzylamine exactly under the literature condi-
tion, but the reaction was not completed and 90% of the starting
material was recovered unchanged (Table 1, entry 23). From this
study, it can be concluded, that this reaction requires stoichiometric
quantities of Mo(CO)6.
Table 1
Optimization of different parameters for aminocarbonylation reactiona
In order to investigate the effect of different complexing agents
on the reactivity of Mo(CO)6, we decided to modify the reaction
conditions with the addition of other ligands and additives, which
are tabulated in Table 2. The reaction of iodobenzene and benzyl-
amine was performed in the presence of Ph3P, cycloheptatriene,
ortho-diaminobenzene, silicadiphenyl phosphinite (SDPP), SiO2,
mesitylene, and norbornadiene (NBD) as complexing agents.
Among these reactions, the shortest reaction time was obtained in
the presence of NBD (Table 2, entry 7). In order to highlight the
effect of NBD as the most suitable complexing agent with Mo(CO)6
on this reaction, its rate enhancement was also studied on the re-
action of 4-iodoanisole as a less reactive aryl halide. This study
showed again that the combination of NBD and TBAB is very suit-
able for the quantitative formation of the corresponding amide
within 5 h (Table 2, entry 11). However, when TBAB or NBD is used
alone in this reaction, neither of these reactions was completed
(Table 2, entries 12 and 13). The reaction of 4-iodoanisole with
benzylamine was carried out with Mo(CO)4(nbd) complex prepared
according to the literature15 as a source of carbonyl. The reaction
was completed with quantitative formation of the amino-
carbonylation product after 8 h (Table 2, entry 10).
Instead of Mo(CO)6, we also used tungsten hexacarbonyl as
a source of CO in the reaction of iodobenzene and benzylamine
under the optimized conditions, which were obtained for the
Mo(CO)6 reactions. The results of this study are shown in Table 3.
According to these results, the combination of W(CO)6 and com-
plexing agents such as cycloheptatriene, NBD, and mesitylene in
comparison to the similar reactions with Mo(CO)6, suffer from
longer reaction times (Table 3, entries 1e3) and in the case of using
NBD, the reaction was not completed (Table 3, entry 2).
O
I
Base, Solvent
NHBn
3aa
Bn-NH2
2a
Mo(CO)6
°
120- 140 C
1a
Entry
Base
Solvent
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
DBU
Diglyme
2
47
56
45
52
31
50
30
42
n-Pr3N
DABCO
n-Pr3N
n-Pr3N
DABCO
DBU
n-Pr3N
DABCO
DABCO
DABCO
K2CO3
NaOH
Cs2CO3
(PhCH2)3N
DABCO
DABCO
DABCO
d
Diglyme
10
Diglyme
1
TBAB
3
BMIMBr
3
TBAB
3
Diglyme, TBAB
Diglyme, TBAB
Diglyme, TBAB
TEAC
Diglyme, TBAB
Diglyme, TBAB
Diglyme, TBAB
Diglyme, TBAB
Diglyme, TBAB
DMSO, TBAB
DMF, TBAB
Toluene, TBAB
d
2
2
9
45 min
85
10
11
12
13
14
15
16
17
18e
19c
20c
21d
22d
23
10
10
2
2
2
Trace
10f
70
61
80
53
27
48
36
9
5:30
2:15
12
24
24
6
23
41
55
d
Diglyme, TBAB
Diglyme, TBAB
Diglyme, TBAB
Diglyme, TEAC
DABCO
DABCO
n-Bu3N
7
3
50
Traceg
a
Reaction conditions: 1.0 mmol of iodobenzene, 1.0 mmol of Mo(CO)6, benzyl-
amine (1.0 mmol), base (3.0 mmol), 2 mL of solvent at 140 ꢀC.
b
Isolated yield.
c
The amount of used benzylamine is 4 mmol in entries 19 and 20.
The amounts of used base are 2 and 1 mmol in entries 21 and 22, respectively.
d
According to the results obtained from the reaction of Mo(CO)6
and different complexing agents, the use of NBD was found to be
most suitable. We therefore applied it as the complexing agent for
the aminocarbonylation of iodobenzene and different aromatic and
aliphatic amines. Using an aliphatic amine such as n-octylamine,
e
Temperature of the reaction is 120 ꢀC.
The reaction was performed using 0.2 equiv of Mo(CO)6.
f
The reaction condition used was exactly as reported in the literature:14
0.6 mmol of iodobenzene, 0.1 mmol of Mo(CO)6, 0.5 mmol of benzylamine,
g
0.55 mmol of n-Bu3N, 0.1 mmol of Et4NCl, diglyme (5 mL) at 150 ꢀC.

420
N. Iranpoor et al. / Tetrahedron 69 (2013) 418e426
Table 3
The study of effect of tungsten carbonyl in the reaction of iodobenzene with ben-
zylamine in the presence of the different ligandsa
Table 2
O
Optimization of the conditions for the reaction of iodobenzene and 4-iodoanisole
with benzylamine in the presence of the different ligandsa
I
NHBn
DABCO, TBAB
W(CO)6
BnNH2
O
°
diglyme, Additive, 140 C
I
DABCO, diglyme
NHBn
1a
2a
3aa
BnNH2
°
reagents, 140 C
R
R
Entry
Ligand
Time (h)
Yieldb (%)
1
2
3
Cycloheptatriene
NBD
Mesitylene
6
4
8
100
80
100
R: H, OCH3
Entry
AreX
Time (h) Reagents
Yieldb (%)
100 (85)
a
Reaction conditions: 1.0 mmol of iodobenzene, 1.0 mmol of W(CO)6, 1.0 mmol
of benzylamine, 3.0 mmol of DABCO, 1.0 mmol of TBAB, 1.0 mmol of ligand and 2 mL
of diglyme at 140 ꢀC.
I
I
1
2
2
Mo(CO)6, Ph3P, TBAB
b
Conversion based on GC analysis.
Mo(CO)6, cycloheptatriene,
TBAB
1:30
100 (82)
100 (81)
the n-octylbenzamide was generated in excellent yield (Table 4,
entry 1). The cross-coupling reaction proceeded for aniline and
aniline-bearing either an electron-withdrawing or an electron-
donating group at the para-position. In the presence of eNO2 as an
electron-withdrawing group on aniline, the reaction was not pos-
sible. While the reaction of iodobenzene and 4-methoxyaniline
proceeded successfully (Table 4, entry 6). Imidazole as an aro-
matic amine did not react under this condition probably due to the
shared electron lone pair in aromaticity of aromatic compound,
which lowers the nucleophilicity of the imidazole. The secondary
aniline and benzylamine were suitable amines in this reaction
(Table 4, entries 4 and 8). Among these amines, aniline and ben-
zylamine were selected as suitable amines (Table 4, entries 2 and 3).
The results are shown in Table 4.
Having the optimized conditions in hand, 1.0 mmol of aryl ha-
lide, 1.0 mmol of Mo(CO)6, 1.0 mmol of benzylamine or 1.0 mmol of
aniline, 3.0 mmol of DABCO, 1.0 mmol of NBD, and 1.0 mmol of
TBAB in 2 mL of diglyme at 140 ꢀC, the cross-coupling reaction
proceeded efficiently for iodobenzene and iodobenzenes bearing
either an electron-withdrawing or an electron-donating group at
the para-position (Table 5, entries 1e3, 12 and 13). The methodol-
ogy was further extended to the coupling of sterically hindered aryl
halides such as 2-iodotoluene and 1-iodonaphthalene and ob-
served to be also viable partners for the coupling reaction (Table 5,
entries 4 and 5, 14). The applicability of this system was developed
I
Mo(CO)6,
ortho-diaminobenzene, TBAB
3
2:10
I
I
I
I
I
I
4
50 min
50 min
45 min
40 min
2
Mo(CO)6, SDPP, TBAB
Mo(CO)6, SiO2, TBAB
Mo(CO)6, TBAB
100 (87)
100 (87)
100 (90)
100 (90)
100 (85)
100 (87)
100 (82)
5
6
7
Mo(CO)6, NBD, TBAB
Mo(CO)6, mesitylene, TBAB
Mo(CO)4nbd, TBAB
Mo(CO)4nbd, TBAB
8
9c
10c
2
to aryl bromides and vinyl bromide.
b-Bromostyrene and 1-
bromonaphthalene reacted successfully both with benzylamine
and aniline to form the corresponding amide (Table 5, entries 10
and 11, 15 and 16). 5-Bromopyrimidine as the heteroaromtic com-
pound performed smoothly in the amidation reaction with ben-
zylamine (Table 5, entry 7). The coupling of benzylamine with 4-
cynao- and 4-chloro-substituted bromobenezene did not proceed
to completion and obtained in moderate to low yield, respectively
(Table 5, entries 6 and 8). The cross-coupling was also applicable to
benzyl bromide, with the corresponding product obtained in good
yield (Table 5, entry 17). We tried this method for the coupling of
benzylamine with bromobenzene but the reaction did not proceed,
even in a sealed tube.
8
11
12
5
Mo(CO)6, NBD, TBAB
Mo(CO)6, NBD
100 (85)
73 (64)
20
13
20
Mo(CO)6, TBAB
70 (61)
Although the mechanism for this reaction is unclear, we pro-
posed the following mechanism on the basis of the literature.13 In
the first step, the complex of molybdenum tetracarbonyl with 2,2,1-
bicycloheptadiene [Mo(CO)4(nbd) (A)] is formed in the presence of
n-Bu4NBr and/or in the absence of it. However, n-Bu4NBr acceler-
ated the rate of the formation of the complex A. Then, the complex
B is formed in the presence of benzylamine. The two possibilities
have been considered for the formation of amide as shown in
Scheme 1. One involves oxidative addition of aryl halide C and
a
Reaction conditions: 1 mmol of aryl halide, 1.0 mmol of Mo(CO)6, 1.0 mmol of
benzylamine, 3.0 mmol of DABCO, 1.0 mmol of TBAB, 1.0 mmol of ligand, and 2 mL
of diglyme at 140 ꢀC.
b
Conversion yield based on GC analysis and isolated yields are in the parenthesis.
Mo(CO)4(nbd) of 1 mmol was used instead of Mo(CO)6.
c

N. Iranpoor et al. / Tetrahedron 69 (2013) 418e426
421
Table 4
Reaction of different amines in the aminocarbonylation reactiona
O
I
NBD, DABCO, TBAB
NR1R2
R1R2NH
Mo(CO)6
°
diglyme,140 C
R1: n-Octyl, PhCH2, Ph, 4-NO2Ph, 4-CH3OPh
R2: H, CH3
Entry
1
Amine
Product
Time (h)
Yieldb (%)
O
Octyl-n
N
H
n-Octyl NH2 2b
1
83
87
3ab
3ac
O
NH2
N
H
2
2:35
2c
O
NH2
N
H
3
4
40 min
90
78
2a
3aa
O
NH(CH3)
N
CH3
2
2d
3ad
NH2
5
6
d
12
d
O2N
2e
OCH3
NH2
O
N
H
2
85
H3CO
2f
3af
H
N
7
8
d
24
d
N
2g
O
NH(CH3)
N
CH3
2:30
87
2h
3ah
O
NH2
N
H
9
2
90
H3CO
OCH3
(continued on next page)
2k
3ak

422
N. Iranpoor et al. / Tetrahedron 69 (2013) 418e426
Table 4 (continued )
Entry
Amine
Product
Time (h)
45 min
Yieldb (%)
O
NH2
CH3
NH
10
81
2l
3al
Cl
O
NH2
NH
11
1:15
67
Cl
2m
3am
a
Reaction conditions: 1.0 mmol of iodobenzene, 1.0 mmol of Mo(CO)6, 1.0 mmol of amine, 3.0 mmol of DABCO, 1.0 mmol of TBAB, 1.0 mmol of NBD, and 2 mL of diglyme at
140 ꢀC.
b
Isolated yield.
Table 5
Aminocarbonylation of organic halides using Mo(CO)6 and benzylamine in the presence of NBD and TBABa
Entry
AreX
Product
Time (h)
40 min
Yieldb (%)
O
I
NHBn
1
90
1a
3aa
O
I
NHBn
NHBn
2
1:35
88
H3C
H3C
1b
3ba
O
I
3
4
5
85
83
H3CO
H3CO
1c
3ca
O
I
NHBn
CH3
1:30
CH3
1d
1e
3da
O
NHBn
I
5
45 min
90
3ea
O
Br
NHBn
6
7
2
65
75
NC
NC
3fa
1f
O
Br
N
N
NHBn
40 min
N
N
1g
3ga

N. Iranpoor et al. / Tetrahedron 69 (2013) 418e426
423
Table 5 (continued )
Entry
AreX
Product
Time (h)
Yieldb (%)
O
Br
NHBn
8
2
23
Cl
Cl
1h
3ha
Br
9
d
24
d
1k
O
NHBn
Br
10
3
80
1l
3ea
O
Br
NHBn
11
12
13
30 min
2:35
3
92
87
80
1m
3ma
O
I
NHPh
O
1a
3ac
I
NHPh
H3C
H3C
1b
3bc
O
NHPh
I
14
1
89
1e
3ec
O
Br
NHPh
15
16
1:45
89
75
1m
3mc
O
NHPh
Br
3
1l
3ec
O
Br
17
1
77
NHBn
1n
3na
a
Reaction conditions: 1 mmol of aryl halide, 1.0 mmol of Mo(CO)6, 1.0 mmol of amine, 3.0 mmol of DABCO, 1.0 mmol of TBAB, 1.0 mmol of NBD, and 2 mL of solvent at
140 ꢀC.
b
Isolated yield.

424
N. Iranpoor et al. / Tetrahedron 69 (2013) 418e426
a subsequent insertion of carbon monoxide to generate acylmo-
lybdenum intermediate D. The other pathway involves the gener-
ation of carbamoylmolybdenum intermediate E, followed by
oxidative addition of aryl halide to generate intermediate F. Finally,
the corresponding product is produced.
3.3. General procedure for aminocarbonylation of aryl ha-
lides and aniline with Mo(CO)6
A
mixture of Mo(CO)6 (0.264 g, 1.0 mmol), aryl halide
(1.0 mmol), aniline (0.09 mL, 1.0 mmol), DABCO (0.336 g,
3.0 mmol), TBAB (0.322 g, 1.0 mmol), and NBD (0.1 mL, 1.0 mmol)
in diglyme (2 mL) was heated at 140 ꢀC. After completion, the re-
action mixture was cooled to room temperature and extracted
with ethyl acetate from the aqueous layer, and dried over anhy-
drous Na2SO4, filtered, and concentrated in vacuum. Then the
crude organic mixture was purified by silica gel column chroma-
tography (petroleum ether/ethyl acetate¼4:1) to obtain the de-
sired product.
DABCO
-DABCOH
Mo(CO)4NH2Bn
BnNH2
Mo(CO)4NHBn
B
ArX
Ar
Mo(CO)4
(CO)4MoNHBn
A
Mo(CO)6
X
Mo(CO)3
NHBn
C
-CO
Mo(CO)5Br Bu4N
3.4. General procedure for the preparation of molybdenum
tetracarbonyl norbornadiene [Mo(CO)4(nbd)]
O
diglyme, 140 o
C
E
X
Bu4N Br Mo(CO)6
ArX
-CO
(CO)3MoNHBn
O
Ar
A molybdenum tetracarbonyl norbornadiene was obtained after
the refluxing of 1.0 mmol of Mo(CO)6 with excess (bicyclo[2.2.1]
hepta-2,5-diene) for 15 h. Bicycloheptadienemolybdenunim tetra-
carbonyl formed pale yellow plates from petroleum ether, which
were stable in air.15
D
X
Ar Mo(CO)3
O
NHBn
O
F
Ar
NHBn
Mo(CO)3X
Scheme 1. Proposed mechanism.
3.5. General procedure for aminocarbonylation of aryl ha-
lides and benzylamine with Mo(CO)4(nbd)
In conclusion we have reported an efficient method for the
aminocarbonylation of aryl, benzyl, and styryl iodides and bro-
mides using Mo(CO)6 in the presence of NBD as the activating li-
A mixture of Mo(CO)4(nbd) (0.328 g, 1.0 mmol), aryl halide
(1.0 mmol), benzylamine (0.11 mL, 1.0 mmol), DABCO (0.336 g,
3.0 mmol), and TBAB (0.322 g, 1.0 mmol), in diglyme (2 mL) was
heated at 140 ꢀC. After completion, the reaction mixture was cooled
to room temperature and extracted with ethyl acetate from the
aqueous layer, and dried over anhydrous Na2SO4, filtered, and
concentrated in vacuum. Then the crude organic mixture was pu-
rified by silica gel column chromatography (petroleum ether/ethyl
acetate¼4:1) to obtain the desired product.
gand. The use of NBD as
a ligand for Mo(CO)6 produces
Mo(CO)4(nbd) as an efficient source of CO for performing the
aminocarbonylation reaction.
3. Experimental section
3.1. General
Spectral data for the products:
Melting points were determined and recorded in open capil-
laries with Buchi B-545 melting point instrument and were not
corrected. FTIR spectra were run on a Shimadzu FTIR-8300 spec-
trophotometer. 1H and 13C NMR spectra were recorded on a Brucker
Avance DPX-250 spectrometers using tetramethyl silane (TMS) as
internal standard in pure deuterated solvents. Chemical shifts are
3.5.1. N-Benzylbenzamide (3aa). White solid, mp: 100e103 ꢀC (lit.
mp: 103e104 ꢀC);16 1H NMR (250 MHz, CDCl3) 4.57 (2H, d,
J¼5.6 Hz), 6.37 (1H, br s), 7.24e7.43 (8H, m), 7.72 (2H, d, J¼7.6 Hz);
13C NMR (62.9 MHz, CDCl3) 43.9, 127.0, 127.4, 127.7, 128.5, 128.6,
131.4, 134.3, 138.3, 167.5; IR (KBr disk)
2840, 1638, 1546, 1320, 715, 684.
n
(cmꢁ1) 3291, 3014, 2922,
given in the
d scale in parts per million (ppm) and coupling con-
stants (J) in hertz. Singlet (s), doublet (d), triplet (t), multiplet (m),
and doublets of doublet (dd) are recorded. The reaction monitoring
was carried out on silica gel analytical sheets or by GC analysis
using a 3-m length column packed with DC-200 stationary phase.
Column chromatography was carried out on the column of silica gel
60 Merck (230e240 mesh) in glass columns (2 or 3 cm diameter)
using 15e30 g of silica gel per 1 g of the crude mixture.
3.5.2. N-Octylbenzamide (3ab). Low mp oil;17a (lit. mp:
43.5e44 ꢀC);17b 1H NMR (250 MHz, CDC13) 0.85e0.90 (3H, m),
1.25e1.32 (10H, m), 1.60 (2H, t, J¼7.5 Hz), 3.37e3.46 (2H, m), 6.37
(1H, br s), 7.40e7.45 (3H, m), 7.74e7.78 (2H, m); 13C NMR
(62.9 MHz, CDCl3) 14.0, 22.6, 26.8, 29.1, 29.2, 29.4, 31.7, 40.4, 126.8,
128.4, 131.2, 134.8, 167.5; IR (KBr disk)
1628, 1527, 750, 721.
n
(cmꢁ1) 3329, 2932, 2835,
3.2. General procedure for aminocarbonylation of aryl ha-
lides and benzylamine with Mo(CO)6
3.5.3. N-Phenylbenzamide (3ac). White solid, mp: 160e162 ꢀC (lit.
mp: 161e164 ꢀC);5g
NMR (250 MHz, CDCl3) 7.07 (1H, t),
H
7.25e7.31 (2H, m), 7.39e7.44 (3H, m), 7.57 (2H, d, J¼7.5 Hz), 7.78
A
mixture of Mo(CO)6 (0.264 g, 1.0 mmol), aryl halide
(2H, d, J¼7.5 Hz), 8.09 (1H, br s); 13C NMR (62.9 MHz, CDCl3) 120.2,
(1.0 mmol), benzylamine (0.11 mL, 1.0 mmol), DABCO (0.336 g,
3.0 mmol), TBAB (0.322 g, 1.0 mmol), and NBD (0.1 mL, 1.0 mmol) in
diglyme (2 mL) was heated at 140 ꢀC. After completion, the reaction
mixture was cooled to room temperature and extracted with ethyl
acetate from the aqueous layer, and dried over anhydrous Na2SO4,
filtered, and concentrated in vacuum. Then the crude organic
mixture was purified by silica gel column chromatography (petro-
leum ether/ethyl acetate¼4:1) to obtain the desired product.
124.5, 127.0, 128.7, 129.0, 131.8, 134.9, 137.9, 165.7; IR (KBr disk) n
(cmꢁ1) 3340, 3039, 2923, 2854, 1650, 1596, 1519, 1434,1319, 1249,
748, 709.
3.5.4. N-Methyl-N-phenylbenzamide
(3ad). Yellow
oil;
bp:
152e154/2.0 Torr, (lit. bp: 121 ꢀC/1.0 Torr);18a,b 1H NMR (250 MHz,
CDCl3) 3.48 (3H, s), 7.03 (2H, d, J¼8.8 Hz), 7.12e7.30 (8H, m); 13C
NMR (62.9 MHz, CDCl3) 38.3, 126.4, 126.8, 127.7, 128.6, 129.1, 129.5,

N. Iranpoor et al. / Tetrahedron 69 (2013) 418e426
425
135.8, 144.9; IR (KBr disk)
1486, 1360, 1302, 1105, 704, 684, 590.
n
(cmꢁ1) 3056, 2921, 2850, 1644, 1594,
CDCl3) 4.47 (2H, d, J¼5.8 Hz), 6.50 (1H, br s), 7.16e7.22 (6H, m),
7.33e7.39 (3H, m), 7.67e7.73 (2H, m), 8.13e8.17 (1H, m); 13C NMR
(62.9 MHz, CDCl3) 43.9, 124.6, 124.9, 125.4, 126.3, 127.0, 127.4, 127.7,
3.5.5. N-(4-Methoxyphenyl)benzamide (3af). White solid, mp:
150e152 ꢀC (lit. mp: 154e155 ꢀC);19 1H NMR (250 MHz, CDCl3)
3.81 (3H, s), 6.89 (2H, d, J¼9.0 Hz), 7.46e7.55 (5H, m), 7.83 (1H, br
s), 7.85 (2H, d, J¼7.9 Hz); 13C NMR (62.9 MHz, CDCl3) 55.4, 114.2,
128.2, 128.7, 130.1, 130.5, 133.6, 134.2, 138.2, 169.4; IR (KBr disk)
n
(cmꢁ1) 3265, 3014, 2921, 2846, 1633, 1526, 773, 694.
3.5.14. N-Benzyl-4-cyanobenzamide (3fa). White solid; mp:
143e146 ꢀC (lit. mp: 150e151 ꢀC);22a,b 1H NMR (250 MHz, CDCl3)
4.55 (2H, d, J¼6.0 Hz), 6.86 (1H, br s), 7.26e7.37 (5H, m), 7.66 (2H, d,
J¼8.5 Hz), 7.86 (2H, d, J¼8.5 Hz); 13C NMR (62.9 MHz, CDCl3) 44.2,
114.9, 118.0, 127.6, 127.8, 128.6, 131.7, 132.3, 137.6, 138.2, 165.6; IR
122.1, 126.9, 128.7, 131.6, 135.0, 135.3, 156.6, 166.4; IR (KBr disk)
n
(cmꢁ1) 3330, 2930, 2837, 1651, 1521, 1410, 1243, 1029, 820, 720,
700.
3.5.6. N-Methyl-N-benzylbenzamide
(3ah). Yellow
oil;
bp:
(KBr disk) n
(cmꢁ1) 3311, 3100, 2921, 2855, 2223, 1642, 1549, 1490,
213e214/10 Torr, (lit. bp: 212 ꢀC/10 Torr);14c 1H NMR (250 MHz,
862, 718, 690, 667.
CDCl3) 2.78 (1.5H, br s), 2.94 (1.5H, br s), 4.43 (1H, br s), 4.67 (1H, br
s), 7.09e7.39 (10H, m); IR (KBr disk)
1635, 1496, 1450, 1388, 1256, 1064, 702.
n
(cmꢁ1) 3031, 2931, 2852,
3.5.15. N-Benzylpyrimidine-5-carboxamide
(3ga). Solid,
mp:
119e122 ꢀC; 1H NMR (250 MHz, CDCl3) 4.53 (2H, d, J¼5.5 Hz),
6.98 (1H, br s), 7.12e7.33 (5H, m), 9.03 (2H, br s), 9.17 (1H, br s);
13C NMR (62.9 MHz, CDCl3) 44.1, 127.7, 127.8, 128.8, 137.2, 155.7,
3.5.7. N-(4-Methoxybenzyl)benzamide (3ak). White solid; mp:
82e85 ꢀC (lit. mp: 87e88 ꢀC);14b 1H NMR (250 MHz, CDCl3) 3.71
(3H, s), 4.48 (2H, d, J¼5.4 Hz), 6.38 (1H, br s), 6.79 (2H, d,
J¼8.6 Hz), 7.19 (2H, d, J¼8.4 Hz), 7.30e7.44 (3H, m), 7.69 (2H, d,
J¼8.2 Hz); 13C NMR (62.9 MHz, CDCl3) 42.5, 54.2, 113.1, 125.9,
160.2, 163.5; IR (KBr disk)
n
(cmꢁ1) 3294, 3031, 2923, 2831, 1643,
1589, 1519, 1458, 1411, 1365, 1288, 1172, 802, 756, 702, 632. Elem.
Anal. found: C, 67.39; H, 5.21; N, 19.50; calcd: C, 67.60; H, 5.16; N,
19.71.
127.5, 128.2, 129.2, 130.4, 133.3, 158.0, 166.2; IR (KBr disk) n )
(cmꢁ1
3317, 2908, 2839, 1643, 1519, 1434, 1350, 1296, 1242, 1180, 1026,
810, 709, 655.
3.5.16. N-Benzyl-4-chlorobenzamide (3ha). Solid; mp: 140e146 ꢀC
(lit. mp: 162 ꢀC);23 1H NMR (250 MHz, CDCl3) 4.55 (2H, d, J¼5.5 Hz),
6.38 (1H, br s), 7.18e7.33 (7H, m), 7.65 (2H, d, J¼8.34 Hz); 13C NMR
(62.9 MHz, CDCl3) 44.0, 127.7, 127.9, 128.4, 128.6, 132.7, 137.5, 138.1,
147.2, 167.6; IR (KBr disk)
1554, 1488, 1312, 1089, 839, 708, 667.
3.5.8. N-(2-Methylphenyl)benzamide (3al). White solid; mp:
132e136 ꢀC (lit. mp: 138 ꢀC);19b 1H NMR (250 MHz, CDCl3) 2.24
(3H, s), 7.05 (1H, t, J¼7.6 Hz), 7.15 (1H, t, J¼7.6 Hz), 7.36e7.44 (4H,
m), 7.47(1H, br s), 7.77e7.81 (3H, m); 13C NMR (62.9 MHz, CDCl3)
17.8, 123.2, 125.4, 126.8, 127.0, 128.8, 129.4, 130.5, 131.8, 134.9, 135.7,
n
(cmꢁ1) 3320, 3045, 2921, 2855, 1643,
3.5.17. (E)-N-Benzylcinnamamide
(3ma). White
solid,
mp:
165.7; IR (KBr disk)
1311, 748, 709.
n
(cmꢁ1) 3240, 3039, 2931, 1643, 1527, 1488,
106e107 ꢀC (lit. mp: 107e109 ꢀC);24 1H NMR (250 MHz, CDCl3) 4.46
(2H, d, J¼5.6 Hz), 6.13 (1H, br s), 6.36 (1H, d, J¼15.6 Hz), 7.17e7.26
(8H, m), 7.39 (2H, d, J¼6.46 Hz), 7.58 (1H, d, J¼15.6 Hz); 13C NMR
(62.9 MHz, CDCl3) 43.8, 120.5, 127.5, 127.8, 127.9, 128.7, 128.8, 129.7,
3.5.9. N-(4-Chlorophenyl)benzamide (3am). White solid, mp:
182e186 ꢀC (lit. mp: 188e190 ꢀC);20 1H NMR (250 MHz, CDCl3)
7.18e7.29 (6H, m), 7.41 (2H, d, J¼8.7 Hz), 7.54 (2H, d, J¼8.8 Hz); 13C
NMR (62.9 MHz, CDCl3) 120.8,126.9,127.8,128.6,128.7,128.9,135.8,
134.7, 138.2, 141.3, 165.8; IR (KBr disk)
n
(cmꢁ1) 3274, 3010, 2930,
2850, 1656, 1614, 1535, 1447, 1340, 1219, 783, 684.
138.5, 163.7; IR (KBr disk)
n
(cmꢁ1) 3271, 2923, 2862, 1728, 1658,
3.5.18. N-Phenyl-4-methylbenzamide (3bc). Solid, mp: 142e146 ꢀC
(lit. mp: 145 ꢀC);25 1H NMR (250 MHz, CDCl3) 2.34 (3H, s), 7.07 (2H,
d, J¼7.5 Hz), 7.19 (d, 2H, J¼7.73 Hz), 7.28 (1H, t), 7.56 (2H, d,
J¼8.3 Hz), 7.70 (2H, d, J¼8.2 Hz), 7.79 (1H, br s); 13C NMR (62.9 MHz,
CDCl3) 21.4, 120.2, 124.4, 127.0, 129.0, 129.4, 132.0, 138.0, 142.3,
1519, 1496, 1180, 1095, 825.
3.5.10. N-Benzyl-4-methylbenzamide (3ba). White solid; mp:
129e132 ꢀC (lit. mp: 133e135 ꢀC);21a,b 1H NMR (250 MHz, CDCl3)
2.34 (3H, s), 4.54 (2H, d, J¼5.7 Hz), 6.87 (1H, br s), 7.14 (2H, d,
J¼7.9 Hz), 7.23e7.32 (5H, m), 7.67 (2H, d, J¼8.1 Hz); 13C NMR
(62.9 MHz, CDCl3) 21.4, 41.9, 126.5, 127.1, 128.3, 128.6, 129.1, 131.5,
165.7; IR (KBr disk)
n
(cmꢁ1) 3358, 2921, 2855, 1647, 1596, 1521,
1433, 1322, 1252, 741, 690.
138.5, 141.8, 167.5; IR (KBr disk)
1549, 1322, 839, 760, 717, 690.
n
(cmꢁ1) 3302, 3014, 2921, 1637,
3.5.19. N-Phenylnaphthalene-1-carboxamide
(3ec). Solid,
mp:
126e130 ꢀC; 1H NMR (250 MHz, CDCl3) 7.17e8.25 (12H, m), 7.85
(1H, br s); 13C NMR (62.9 MHz, CDCl3) 119.9, 124.6, 124.7, 125.0,
125.2, 126.5, 127.3, 128.4, 129.1, 131.0, 133.7, 138.0, 149.0, 165.4; IR
3.5.11. N-Benzyl-4-methoxybenzamide (3ca). White solid;5d mp:
118e122 ꢀC (lit. mp: 124e126 ꢀC);5h 1H NMR (250 MHz, CDCl3) 3.72
(3H, s), 4.49 (2H, d, J¼5.6 Hz), 6.59 (1H, br s), 6.78 (2H, d, J¼8.6 Hz),
7.14 (5H, m), 7.66 (2H, d, J¼8.6 Hz); 13C NMR (62.9 MHz, CDCl3)
43.9, 55.3, 113.6, 126.9, 127.8, 128.4, 128.6, 128.8, 138.5, 162.1, 167.0;
(KBr disk)
n
(cmꢁ1) 3218, 1647, 1591, 1535, 1498, 1438, 1317, 1257,
787, 745, 694. Elem. Anal. found: C, 82.70; H, 5.10; N, 5.56; calcd: C,
82.59; H, 5.26; N, 5.67.
IR (KBr disk)
n
(cmꢁ1) 3255, 3062, 2923, 2839, 1627, 1558, 1504,
3.5.20. (E)-N-Phenylcinnamamide (3mc). Solid; mp: 136e139 ꢀC
(lit. mp: 150e153 ꢀC);26 1H NMR (250 MHz, CDCl3) 6.59 (1H, d,
J¼15.5 Hz), 6.89e7.32 (9H, m), 7.57 (1H, s), 7.62 (1H, d, J¼15.5 Hz),
8.28 (1H, br s); 13C NMR (62.9 MHz, CDCl3) 120.2, 121.1, 124.4, 127.9,
1450, 1411, 1326, 1249, 1180, 840, 717, 686.
3.5.12. N-Benzyl-2-methylbenzamide (3da). White solid; mp:
90e95 ꢀC (lit. mp: 105e106 ꢀC);12b 1H NMR (250 MHz, CDCl3) 2.37
(3H, s), 4.59 (2H, d, J¼5.7 Hz), 6.11 (1H, br s), 7.13e7.34 (9H, m); 13C
NMR (62.9 MHz, CDCl3) 19.8, 43.8, 125.6, 126.6, 127.5, 127.8, 128.7,
128.8, 129.0, 129.9, 134.6, 138.2, 142.2, 164.5; IR (KBr disk) n )
(cmꢁ1
3290, 2930, 2854, 1661, 1623, 1594, 1544, 1490, 1440, 1348, 1247,
1185, 860, 760.
129.8, 131.0, 136.1, 136.2, 138.2, 169.9; IR (KBr disk)
3024, 2923, 1627, 1519, 1450, 1365, 1272, 740, 686.
n
(cmꢁ1) 3271,
3.5.21. N-Benzyl-2-phenylacetamide (3na). White solid; mp:
116e119 ꢀC (lit. mp: 122 ꢀC);13b 1H NMR (250 MHz, CDCl3) 3.47 (2H,
s), 4.34 (2H, d, J¼5.76 Hz), 6.02 (1H, br s), 7.04e7.34 (10H, m); 13C
NMR (62.9 MHz, CDCl3) 43.3, 44.2, 127.2, 127.3, 127.5, 128.4, 128.8,
3.5.13. N-Benzylnaphthalene-1-carboxamide (3ea). White solid;
mp: 120e123 ꢀC (lit. mp: 125e126 ꢀC);12c 1H NMR (250 MHz,

426
N. Iranpoor et al. / Tetrahedron 69 (2013) 418e426
6. Tsuji, Y.; Yoshii, S.; Ohsumi, T.; Kondo, T.; Watanabe, Y. J. Organomet. Chem. 1987,
130.2, 132.7, 138.0, 175.2; IR (KBr disk)
2855, 1643, 1554, 1488, 1312, 1089, 839, 708, 667.
n
(cmꢁ1) 3320, 3045, 2921,
331, 379e385.
7. Kondo, T.; Okada, T.; Mitsudo, T. Organometallics 1999, 18, 4123e4127.
8. (a) Ju, J.; Jeong, M.; Moon, J.; Jung, H. M.; Lee, S. Org. Lett. 2007, 9, 4615e4618;
(b) Wan, Y.; Alterman, M.; Larhed, M.; Hallberg, A. J. Org. Chem. 2002, 67,
6232e6235.
Acknowledgements
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We are grateful to the research council of Shiraz University for
supporting this work.
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